Unlike most core resource facilities appended to program project grants, the new Validation Core proposed here is more than a detached support unit. The purpose of this core is to assure that the signal obtained from the experiments performed in the major projects is valid, a necessary step before deeper studies, in particular those bound for the clinic, can be undertaken. We will validate the probes and methods produced in several ways, including a) characterization of nanomaterial targeting moieties through use and/or development of suitable binding affinity assays in vitro; b) determination of selective targeting of nanomaterials in cellule through fluorescent or radioactive means; c) ex vivo pharmacokinetic studies in relevant animal models; d) in vivo pharmacokinetic and pharmacodynamic studies through small animal imaging and e) provision of all animalrelated services, including pre-Good Laboratory Practice (GLP) toxicity assays, in collaboration with the Department of Molecular and Comparative Pathobiology (Drs. Gabrielson and Brayton). We will further perform correlation of any imaging studies with traditional ex vivo and histological approaches and will also attempt to cross-correlate, when practical and useful, the MR-based imaging findings with other modalities, especially radionuclide-based and those that employ optical (fluorescence and bioluminescence) imaging. In that regard the validation core will perform a certain degree of its own research - rather than merely providing routine services - but that research will always be related to the major projects. Because validation is critical to any imaging study, the integration of this core to the projects is clear. The goal of this core is to enable the scientists performing the studies of the major projects to focus on the most complex aspects of their work, Interfacing closely with the core not only to procure routine services, but to assure the validity of their results.